Re: [PATCH] raid5: guarantee enough stripes to avoid reshape hang

[NeilBrown <neilb@suse.com>]

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On Wed, Aug 31 2016, Shaohua Li wrote:

> If there aren't enough stripes, reshape will hang. We have a check for
> this in new reshape, but miss it for reshape resume, hence we could see
> hang in reshape resume. This patch forces enough stripes existed if
> reshape resumes.
>
> Signed-off-by: Shaohua Li <shli@fb.com>

I'm really surprised that this was missing, but it certainly appears
that it was.

 Reviewed-by: NeilBrown <neilb@suse.com>

thanks!


NeilBrown


> ---
>  drivers/md/raid5.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 62febe8..2fdb97b 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -6639,6 +6639,16 @@ static struct r5conf *setup_conf(struct mddev *mddev)
>  	}
>  
>  	conf->min_nr_stripes = NR_STRIPES;
> +	if (mddev->reshape_position != MaxSector) {
> +		int stripes = max_t(int,
> +			((mddev->chunk_sectors << 9) / STRIPE_SIZE) * 4,
> +			((mddev->new_chunk_sectors << 9) / STRIPE_SIZE) * 4);
> +		conf->min_nr_stripes = max(NR_STRIPES, stripes);
> +		if (conf->min_nr_stripes != NR_STRIPES)
> +			printk(KERN_INFO
> +				"md/raid:%s: force stripe size %d for reshape\n",
> +				mdname(mddev), conf->min_nr_stripes);
> +	}
>  	memory = conf->min_nr_stripes * (sizeof(struct stripe_head) +
>  		 max_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
>  	atomic_set(&conf->empty_inactive_list_nr, NR_STRIPE_HASH_LOCKS);
> -- 
> 2.8.0.rc2
>
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